In vivo stable isotope labeling and computer-assisted metabolic flux analysis were used to investigate the metabolic pathways in petunia (Petunia hybrida) cv Mitchell leading from Phe to benzenoid compounds, a process that requires the shortening of the side chain by a C2 unit. Deuterium-labeled Phe (2H5-Phe) was supplied to excised petunia petals. The intracellular pools of benzenoid/phenylpropanoid-related compounds (intermediates and end products) as well as volatile end products within the floral bouquet were analyzed for pool sizes and labeling kinetics by gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry. Modeling of the benzenoid network revealed that both the CoA-dependent, β-oxidative and CoA-independent, non-β-oxidative pathways contribute to the formation of benzenoid compounds in petunia flowers. The flux through the CoA-independent, non-β-oxidative pathway with benzaldehyde as a key intermediate was estimated to be about 2 times higher than the flux through the CoA-dependent, β-oxidative pathway. Modeling of 2H5-Phe labeling data predicted that in addition to benzaldehyde, benzylbenzoate is an intermediate between l-Phe and benzoic acid. Benzylbenzoate is the result of benzoylation of benzyl alcohol, for which activity was detected in petunia petals. A cDNA encoding a benzoyl-CoA:benzyl alcohol/phenylethanol benzoyltransferase was isolated from petunia cv Mitchell using a functional genomic approach. Biochemical characterization of a purified recombinant benzoyl-CoA:benzyl alcohol/phenylethanol benzoyltransferase protein showed that it can produce benzylbenzoate and phenylethyl benzoate, both present in petunia corollas, with similar catalytic efficiencies.
采用体内稳定同位素标记和计算机辅助代谢通量分析,研究了从苯丙氨酸到苯环化合物的代谢途径,这个过程需要将侧链缩短一个C2单元的方式。氘标记的苯丙氨酸(2H5-Phe)被提供给切除的矮牵牛(Petunia hybrida)Mitchell品种的花瓣。通过气相色谱-质谱和液相色谱-质谱分析花香中的苯环/苯丙素相关化合物(中间产物和终产物)以及挥发性终产物的细胞内库大小和标记动力学。苯环网络的建模表明,CoA依赖性β氧化和CoA非依赖性非β氧化途径都对矮牵牛花中苯环化合物的形成做出了贡献。以苯甲醛为关键中间体的CoA非依赖性非β氧化途径通量估计约为CoA依赖性β氧化途径通量的2倍。2H5-Phe标记数据的建模预测,除了苯甲醛外,苄基苯甲酸酯是L-苯丙氨酸和苯甲酸之间的中间体。苄基苯甲酸酯是苄基醇苯甲酰化的产物,在矮牵牛花瓣中检测到了其活性。利用功能基因组学方法,从矮牵牛Mitchell品种中分离了编码苯丙醇/苄醇苯甲酰转移酶的苯乙酰-CoA:苄醇/苯乙醇苯甲酰转移酶的cDNA。对纯化重组苯乙酰-CoA:苄醇/苯乙醇苯甲酰转移酶蛋白的生化特性进行了表征,表明它可以产生苄基苯甲酸酯和苯乙基苯甲酸酯,两者在矮牵牛花冠中具有类似的催化效率。